The present invention relates to froth flotation processes for recovery of gold, silver and platinum group metals (PGM) from base metal ores. More particularly, it relates to improved collectors comprising certain synergistic combinations of allylalkylthionocarbamates and dithiophosphates which exhibit an excellent selective recovery of gold, silver and platinum group metals under neutral to alkaline conditions.
Froth flotation is one of the most widely used processes for beneficiating ores containing valuable minerals and is more fully described in U.S. Pat. No. 4,584,097, hereby incorporated herein by reference
The success of a flotation process depends a great degree on the reagent(s) called collector(s) that impart(s) selective hydrophobicity to the valuable mineral that has to be separated from other minerals Thus, the flotation separation of one mineral species form another depends upon the relative wetability of mineral surfaces by water. Typically, the surface free energy is purportedly lowered by the adsorption of heteropolar collectors. The hydrophobic coating thus provided acts, in this explanation, as a bridge so that the mineral particles may be attached to an air bubble. The practice of this invention is not, however, limited by this or other theories of flotation.
Xanthates, alkyl xanthogen alkyl formates, bis alkyl xanthogen formates, dialkylthionocarbamates, hydrocarboxycarbonyl thionocarbamates, etc. have been shown to be useful collectors in froth flotation processes. Most of these known collectors, however, are known to suffer from at least one deficiency which prevents them from being used universally for the recovery of metals from each and every ore requiring refining, such as pH dependency, affinity for some metals versus others etc.
The use of mixtures of dithiophosphates and dialkylthionocarbamates as collectors for the recovery of copper from copper-containing ores is taught in U.S. Pat. No. 3,925,218. This patent however, does not include the allyl alkylthionocarbamates nor does it recognize the selectivity of this mixture for gold, silver and platinum group metals.
Accordingly, it is an object of the present invention to provide an improved collector and flotation process for the beneficiation of minerals employing froth flotation methods for the selective recovery of gold, silver and platinum group metals from ore.